As a technique of heating substrates such as semiconductor substrates or flat panel display (FPD) substrates, a technique has been known in which an oscillating magnetic field having a high frequency is generated through an induction coil supplied with a high frequency power and heating elements disposed within the oscillating magnetic field generate heat through an induced current (electromagnetic induction heating), thereby heating the substrates mounted on or close to the heating elements by the heat transferred from the heating elements. In order to apply this technique to a batch processing of a plurality of sheets of substrates, a heat treatment apparatus is proposed in which a plurality of heating elements are vertically disposed in the shape of a shelf within a vacuumized processing vessel and the plurality of heating elements generate heat through the induction coil installed outside the vacuum processing vessel, thereby heating the plurality of sheets of substrates correspondingly disposed with respect to the plurality of heating elements.
For example, it has been known that a vertical film forming apparatus, as a type of heat treatment apparatus, which heats a plurality sheets of substrates using electromagnetic induction heating and supplies each substrate with a source gas to form a film on the surface of the substrate. This film forming apparatus is provided with a support jig which is made of a conductive material and supports the plurality of sheets of substrates within a processing vessel. The support jig is configured to function as a heating element in the electromagnetic induction heating, thus generating a vertical oscillating magnetic field in the processing vessel by an induction coil provided outside the processing vessel and making the support jig generate heat. Then, the supported substrates within the processing vessel are heated. Further, a film forming process is performed by allowing the source gas to flow parallel to the substrates from a gas introduction port disposed at a side of the processing vessel.
However, in such a configuration, the support jig for supporting the substrates is enlarged as the substrates have an enlarged diameter. Thus, it is difficult for the support jig to generate heat uniformly through the induction coil provided outside the processing vessel. Further, it is also difficult to satisfactorily maintain in-plane or inter-plane temperature uniformity of the substrates heated by the heat transferred from the support jig. In addition, films or reaction products attached on the support jig in the film forming process are eventually peeled off and thus become a dust generating source. Thus, a cleaning process, in which the support jig is detached from the processing vessel and accretions attached on the support jig are removed, is periodically needed. However, the support jig is enlarged in this configuration as the substrates have an enlarged diameter. Therefore, it is difficult to detach and attach the support jig from and to the processing vessel and the cost of cleaning solutions and the like is increased in cleaning the support jig.
In comparison, although another type of heat treatment apparatus is a vertical film forming apparatus, a plurality of heating elements corresponding to respective substrates are provided, contrary to the integrated heating element configured to generate heat through the induction coil provided outside the processing vessel. Further, the plurality of heating elements is configured to be supported by a support jig made of an insulating material such as quartz or the like. Since an induced current does not flow in the support jig made of an insulating material and thus the support jig does not generate heat, a few films or reaction products are attached. In addition, the heating elements are separated corresponding to the respective substrates. Thus, it is convenient to attach and detach the heating elements to and from the support jig and to clean the heating elements. The substrates are respectively heated by the heat transferred from the corresponding heating elements, and so it is possible to adjust an in-plane temperature distribution of the substrates by changing the shape of the heating elements or a distance between the heating elements and the substrates. Further, in such a configuration, since the support jig rotates with the heating elements supported therein, it is possible to obtain in-plane temperature uniformity of a large diameter substrate.
In addition, as a technique in which the heating elements corresponding to respective substrates are detachably installed to the support jig and the support jig is configured to be rotatable, it has been known that an electromagnet supplied with high frequency power, as a mechanism for generating a horizontal oscillating magnetic field, is disposed outside a processing vessel. Also, it has been known that an induction coil is disposed inside a processing vessel to be closer to the heating elements, thereby improving the efficiency of electromagnetic induction heating.
However, in the techniques as described above, the support jig for supporting and rotating the heating elements needs a strong structure for holding and supporting the plurality of heating elements. For this reason, since the support jig occupies a large space within the processing vessel, the heating elements are spaced apart from the induction coil by the occupied space. In the electromagnetic induction heating, the heating efficiency depends on a distance between the induction coil and the heating elements. Thus, it is possible to increase the heating efficiency by causing the heating elements to get closer to the induction coil. However, in this technique, since it is necessary to space the heating elements and the induction coil apart from each other by the occupied space of the support jig, it is difficult to increase the heating efficiency.
Furthermore, the support jig is made of an insulating material and the support jig itself does not generate heat. However, since the support jig receives heat from the heating elements to have increased temperature, although less than the case of the heating elements, films or reaction products are attached to the support jig in the film forming process and may become a dust generating source. For this reason, it is also necessary to periodically perform a cleaning process on the support jig. Accordingly, the above-described problems still remain making it 1 difficult to detach and attach the support jig from and to the processing vessel thereby increasing the cost of cleaning the support jig.